On the PSP, there is a homebrew called "MagicSave" that would allow you to fix a corrupted save data.
I'm wondering if there is an alternative that would allow me to fix a corrupted save data for the PPSSPP, or an external program that can fix it.
OR, if MagicSave does in fact work for the emulator, how would I go about doing so.

MagicSave itself won't work on PPSSPP, since it doesn't support seplugins (and as a result SED / Gavegame Deemer won't either). I don't know of a way you can fix saves without using a real PSP in some way.

If someone wants to use Magic save to fix outdated PSP savedata(which should generally not happen unless you still have saves from really old PSP or download savedata from sites like gamefaqs) you can now just use PPSSPP built-in function.

Note that it will NOT fix savedata which actually is corrupted/broken as no software will ever help you with that, however games do often use scarry words when simply not recognizing encryption(giving errors like 80110306) and that's really easy to solve.
Just follow this short guide.